This invention relates to the field of traffic engineering, and more particularly, to controlling vehicle traffic at intersections where roads meet.
Vehicle traffic through roadway intersections where roads meet has traditionally been controlled by traffic lights and signage. For example, at a conventional intersection of two roads, a traffic light is positioned to intermittently stop the movement of traffic along one road while traffic proceeds along the other road through the traffic intersection. After a period of time, the traffic light is adjusted to stop movement along the one road and permit movement along the other road. Traffic signs, such as stop signs, are also used to similarly control a conventional traffic intersection. For example, a four-way traffic stop can include stop signs on each road to stop the movement of vehicles on both roads before entering the traffic intersection. Also, a two-way traffic stop can include stop signs on one of the roads to stop the movement of vehicles on that road before entering the traffic intersection.
Roundabouts are another traffic control feature that are used to control vehicle traffic at traffic intersections. In a typical intersection having a roundabout, an island is located at the center of the traffic intersection and one or more roundabout lanes follow a generally circular path around the island. Vehicle traffic approaches the traffic intersection and enters the roundabout lane(s). Vehicle traffic follows the roundabout lane(s) until exiting the traffic intersection along a desired road.
Roundabouts are considered to provide advantages over conventional traffic lights and signs for controlling vehicle traffic. At some intersections, for example, a roundabout may be a safer, more efficient, and/or environmentally better option for controlling traffic than conventional traffic lights and signs. However, constructing roundabouts typically presents additional considerations and other problems. For example, a traffic intersection having a roundabout may occupy a larger amount of roadway space than a conventional traffic intersection without the roundabout. Thus, building a traffic intersection having a roundabout may require more land than a conventional traffic intersection. In addition, the construction of traffic intersections requires substantial manpower, equipment, and resources. For example, the location of a traffic intersection is typically prepared using large and expensive construction machinery. This construction work can take several weeks to complete. And if a conventional traffic intersection is converted into a traffic intersection having a roundabout, this typically requires demolition and/or removal of the existing intersection before a roundabout is constructed. Such removal often requires work by such construction machinery, thereby making such a project costly, both in terms of financial resources and the amount of time the traffic intersection is under construction and mostly unusable. For example, roundabout traffic intersection construction projects can take from as little as several weeks up to several months, depending on the complexity of the intersection. In addition, the intersection may be unusable during some or all of the construction. Also, if additional land is required to add a roundabout, acquiring the additional land can add to the time and expense associated with the construction project.